The chitinase-like protein called chitinase 3-like-1 (Chi3l1; also called Chil1 in mice and YKL-40 in man) has been implicated in asthma and cancer, e.g., lung cancer. It has been demonstrated that the levels of circulating Chi3l1 are increased in human asthma where they correlate with disease severity. The levels of circulating YKL-40 are increased in many malignancies including cancers of the prostate, colon, rectum, ovary, kidney, breast, glioblastomas and malignant melanoma. In these diseases, the levels of YKL-40 frequently correlate directly with disease progression and inversely with disease-free interval and survival.